This invention relates to a device for picking up sheets from a magazine in a packaging machine. The invention is useful for picking up labels in labelling machines.
Prior art labelling machines are substantially of two types, one with a movable label magazine, and one with a fixed or stationary label magazine. The device intended to pick up the labels from the magazine comprises generally a rotating drum, onto peripheral portions whereof a coating of glue is applied by means of suitable gumming rollers. If the magazine is of the movable type, the withdrawal is effected by imparting to that magazine an oscillatory movement such that each label adhere without slippage on a corresponding area of the drum provided with glue, to remain attached thereto. If, by contrast, the magazine is of the fixed type, then the withdrawal is carried out by means of circular sectors or segments, being controlled by camming means to first contact the gumming rollers and then roll over the labels removing them from the magazine which contains them.
Prior art labelling machines are generally affected by functional drawbacks of importance. Frequently, for example, there occurs a relative movement, i.e. slip, between the label magazine and the drum sector provided with glue, thereby the correct withdrawal of the labels may be precluded. In particular for the fixed drum machines, the arrangement of oscillable circular sectors on the drum poses a whole series of additional problems, among which the presence of high stresses in the overcoming of the dead centers by the camming means, as well as the forcibly limited number of circular sectors, i.e. labels on the drum, due to the large angular size of the latter.